On the rounds tab, look on the left hand side of the display for the rounds. The bottom of the column will be a button labeled preferences. Click that. Next, click on edit columns. On mine, I have Level, Duration, Small Blind, and Big Blind.

Or are you referring to the "Blinds Schedule" Screen, displayed in the Game window? If so, right-click when the Blinds Schedule screen is displayed and select "Blinds Schedule Screen Properties". Then press the "Edit Columns" button to change which columns are displayed.

As I said above I do not have a preferences tab in the 'rounds' section, I have removed BOTH limits and antes options from the 'columns' option but they still appear on screen when the screen set gets to that option.